Table 1

Comparison of potencies for endocytosis and inhibition of cAMP accumulation

Drug	EC₅₀
Drug	For endocytosis	For cyclase	Ratio
Etorphine	7.28 ± 1.25 nm	0.16 ± 1.17 nm	45.5
DAMGO	547 ± 69.0 nm	13.0 ± 2.6 nm	42.0
Morphine	>1 mm	30.2 ± 9.0 nm	>30,000

Data from Fig. 4, A and B, were fitted to a four-parameter logistic function to yield the EC₅₀ values shown here, and the ratio of these two values is given.